During neutrophil transmigration (diapedesis), the final step involving migration through the basement membrane is mediated by:
- A CD31 (PECAM-1) interactions alone
- B Neutrophil secretion of proteases (MMP-9, elastase) to degrade basement membrane matrix ✓
- C Selectin-mediated rolling on endothelial cells
- D Integrin-ICAM interactions providing sufficient force for transmembrane passage
Correct answer: B. Neutrophil secretion of proteases (MMP-9, elastase) to degrade basement membrane matrix
Explanation
After firm adhesion (integrin/ICAM) and squeezing through endothelial junctions (aided by CD31/PECAM-1 homophilic interactions), neutrophils must traverse the subendothelial basement membrane. This step requires secretion of metalloproteinases (MMP-9/gelatinase B) and serine proteases (elastase, cathepsin G) to focally degrade collagen IV and laminin in the basement membrane. Selectins mediate only the initial rolling step. CD31 mediates junctional diapedesis, not basement membrane penetration.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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